McDonnell Douglas C-17 Globemaster III C-17A Block 16

Block 16 is the C-17A Globemaster III series upgrade that Boeing introduced in 2005, bringing to the production line a new weather radar, a second-generation fuel tank inerting system, sturdier stabilizer struts and modernized avionics. Like the other C-17 blocks, it did not lead to a new designation: the aircraft remain C-17As, but with a different set of equipment from earlier airframes.

The main source is the manufacturer’s own publication, *Boeing Frontiers*, whose [September 2005 issue](https://web.archive.org/web/2006/https://www.boeing.com/news/frontiers/archive/2005/september/i_ids1.html) (volume 4, number 5) carried Debby Arkell’s article “Boeing continues the C-17's excellence with Block 16 upgrades”. According to that text, Boeing marked the debut of the new configuration with the 9 August delivery of the U.S. Air Force’s 138th C-17. Previously delivered aircraft would not be left behind: they would have the upgrades retrofitted beginning in 2007.

The article lists four groups of changes. All Block 16 aircraft would have a state-of-the-art weather radar system; an improved version of the system that generates inert gas on board for the fuel tanks, called OBIGGS II (Onboard Inert Gas–Generating System); a new, more reliable and stronger stabilizer strut system; and a suite of modernized avionic boxes. None of them changes the aircraft’s size, payload or performance; what changes is what the aircraft can see, how long it takes to prepare and how much it weighs.

The new weather radar, the APS-150, allows pilots to see weather systems up to 320 nautical miles (593 kilometres) ahead, up from the 160 to 200 nautical miles (296 to 370 kilometres) of the previous equipment. According to Boeing Frontiers, it also weighs nearly half as much and uses one third of the power. For a transport aircraft flying long routes and landing on austere airfields, seeing bad weather earlier gives the crew more room to decide.

The second-generation inerting system greatly shortens the aircraft’s preparation: with OBIGGS II, the tanks are inerted in less than one hour, compared with the four to eight hours previously needed. The change also cuts the aircraft’s weight by almost 500 pounds, about 227 kilograms, a saving that adds to that of the radar, which is lighter than its predecessor.

The new configuration was thoroughly tested before its debut: according to the same publication, it logged more than 330 test hours, 175 of them in flight and 155 on the ground.

Block 16 is part of the series of blocks through which the C-17 was updated during production. Before it came Block 12, to which Boeing ties the centre wing fuel tank (the configuration informally known as the C-17A ER). Later, according to the Air Force Association’s magazine, [Air & Space Forces Magazine](https://www.airandspaceforces.com/weapons-platforms/c-17/), came Block 20, which brought together some 60 programs to bring early production aircraft to a common configuration, and Block 21, focused on airspace and identification avionics.

The Boeing source gives neither the total number of aircraft brought up to the Block 16 standard nor the date on which the retrofit of earlier aircraft was completed. Those figures remain open until a reliable source turns up, and this page therefore does not include them.